Marathon of photos: Twitter and Instagram images from the 2013 Chicago Marathon

Amtrak Police has at least 8 officers and two dogs on Canal outside Union Station #ChicagoMarathon pic.twitter.com/M1wuYiXo7J — Diana Novak (@dhnovak) October 13, 2013 US Marshals at Madison and Franklin, say they've stepped up presence at marathons since Boston #ChicagoMarathon pic.twitter.com/g2uNE3GQZe — Diana Novak (@dhnovak) October 13, 2013 It goes from so loud to silent